U.S. patent application number 16/063121 was filed with the patent office on 2020-08-20 for mirror including reflective backlit display.
The applicant listed for this patent is 3M INNOVATIVE PROPERTIES COMPANY. Invention is credited to Kazuhiko Toyooka.
Application Number | 20200262351 16/063121 |
Document ID | 20200262351 / US20200262351 |
Family ID | 1000004854514 |
Filed Date | 2020-08-20 |
Patent Application | download [pdf] |
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United States Patent
Application |
20200262351 |
Kind Code |
A1 |
Toyooka; Kazuhiko |
August 20, 2020 |
MIRROR INCLUDING REFLECTIVE BACKLIT DISPLAY
Abstract
Mirrors including reflective backlit displays are described. In
particular, mirrors including backlit displays with a backlight, a
liquid crystal cell including a liquid crystal layer disposed
between two opposing transparent substrate layers, a first
reflective polarizer, and a second reflective polarizer are
described. The first and second reflective polarizers are each
directly laminated to one of the opposing transparent substrate
layers. Mirrors described herein may be configured as vehicle
rear-view mirrors.
Inventors: |
Toyooka; Kazuhiko; (Yamagata
Prefecture, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
3M INNOVATIVE PROPERTIES COMPANY |
St. Paul |
MN |
US |
|
|
Family ID: |
1000004854514 |
Appl. No.: |
16/063121 |
Filed: |
December 6, 2016 |
PCT Filed: |
December 6, 2016 |
PCT NO: |
PCT/US2016/065183 |
371 Date: |
June 15, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62268908 |
Dec 17, 2015 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G02F 1/133536 20130101;
G02F 2001/133567 20130101; G02B 6/0055 20130101; G02F 2001/133562
20130101; B60R 1/12 20130101; B60R 2001/1215 20130101 |
International
Class: |
B60R 1/12 20060101
B60R001/12; G02F 1/1335 20060101 G02F001/1335; F21V 8/00 20060101
F21V008/00 |
Claims
1. A reflective backlit display, comprising: a backlight; a liquid
crystal cell including a liquid crystal layer disposed between two
opposing transparent substrate layers; a first reflective
polarizer; and a second reflective polarizer; wherein the first and
second reflective polarizers are each directly adjacent to one of
the opposing transparent substrate layers.
2. The reflective backlit display of claim 1, wherein at least one
of the first or second reflective polarizers is a multilayer
reflective polarizer.
3. The reflective backlit display of claim 1, wherein each of the
first or second reflective polarizers is a multilayer reflective
polarizer.
4. The reflective backlit display of claim 3, wherein the two
transparent substrate layers are glass.
5. The reflective backlit display of claim 1, wherein the first and
second reflective polarizers are each directly laminated to one of
the opposing transparent substrate layers.
6. The reflective backlit display of claim 1, wherein the backlight
includes a lightguide, a reflector disposed on the light guide, and
a light source configured to inject light into the lightguide.
7. The reflective backlit display of claim 1, further comprising a
third reflective polarizer, wherein the third reflective polarizer
is disposed on either the first or the second reflective
polarizer.
8. A mirror, comprising: a mirror portion; and a reflective backlit
display portion comprising the reflective backlit display of claim
1; wherein the reflective backlit display is capable of directly
displaying images, and the mirror portion is not.
9. A vehicle, comprising the mirror of claim 8, the mirror being
configured as a rear-view mirror.
10. The mirror of claim 9, wherein the reflective backlit display
portion is greater than 10% but less than 50% of an area of the
mirror.
11. The reflective backlit display of claim 1, wherein the
reflective backlit display includes no absorbing polarizers.
12. The reflective backlit display of claim 1, wherein the
reflective backlit display includes no non-polarization-dependent
partial reflector.
Description
BACKGROUND
[0001] Mirrors are used for many purposes, including for safety,
aesthetics, and sartorial functions.
[0002] Mirrors are commonly used in vehicles to view ambient road
and traffic conditions generally behind the vehicle without needing
to turn the head. Backlit displays utilize a spatial light
modulator to selectively transmit and absorb light. Backlit
displays may display in color or in monochrome.
SUMMARY
[0003] In one aspect, the present description relates to reflective
backlit displays. In particular, the present description relates to
reflective backlit displays including a backlight, a liquid crystal
cell including a liquid crystal layer disposed between two opposing
transparent substrate layers, a first reflective polarizer, and a
second reflective polarizer. The first and second reflective
polarizers are each directly adjacent to one of the opposing
transparent substrate layers.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] FIG. 1 is a front elevation view of a rear-view mirror
including a reflective backlit display.
[0005] FIG. 2 is a side elevation view of a reflective backlit
display stack.
DETAILED DESCRIPTION
[0006] Rear view mirrors in vehicles, and in particular center (or
inside) rear view mirrors may include display elements in order to
provide navigational, status, safety, or other information to a
driver. The inclusion of this information in a center rear view
mirror may be particularly useful because a driver can glance at
such information without losing sight of the road and traffic in
front of the vehicle. Further, a driver routinely scans the mirrors
instinctively, and so important information displayed on the mirror
will be reliably seen by the driver without having to get
accustomed to looking in a new or unusual location.
[0007] Conventional center rear view mirror displays adapt a
conventional display stack by simply adding a vapor coated mirror
(sometimes described as a half- or partial-mirror or reflector) on
the front of the display. Such an adaptation reflects some portion
of the ambient light, creating a mirror-like appearance, but also
reflects the same portion of the light from the convention display
stack back away from the emission surface (the viewing surface) of
the rear view mirror because the vapor coated mirror is a
non-polarization-dependent reflector. This reflection loss is on
top of the conventional losses in a display stack: from both the
front and back absorbing polarizers and also the liquid crystal
layer. Having the mirror-like appearance allows for the full
surface of the mirror to be useful or viewable when the display is
not displaying information. Further, the mirror-like appearance may
be aesthetically preferable by having uniformly appearing rear view
mirror.
[0008] By replacing at least the front absorbing polarizer with a
reflective polarizer, and in some embodiments both the front and
the back absorbing polarizer with two reflective polarizers, the
display stack can incorporate the ambient light reflection
functionality of a partial mirror without the need for additional
layers. Further, the replacement of at least one absorbing
polarizer with reflective polarizers eliminates at least some of
the absorbing elements from the stack. These modifications may
provide for a reflective backlight display with higher brightness
and efficiency than a reflective backlight using a conventional
display stack.
[0009] FIG. 1 is a front elevation view of a rear-view mirror
including a reflective backlit display. Rear-view mirror 100
includes mirror portion 110 and reflective backlit display portion
120 displaying information. Mirror portion 110 and reflective
backlit display portion 120 may have similar appearances. However,
reflective backlit display portion 120 may be capable of directly
displaying generated information or images, while mirror 110 is
not. In some embodiments, mirror portion 110 may be a small portion
of rear-view mirror 100, such as 40%, 30%, or 20% of the surface
area. In some embodiments, mirror portion 110 may be a larger part
of rear-view mirror 100, such as 50%, 60%, 70%, 80%, 90% or more.
In some embodiments, the mirror portion may be between 50% and 90%
of the rear-view mirror. In some embodiments, the display portion
may be 100% of the mirror portion; in other words, the mirror
portion and the display portion may be the same and fill the entire
reflective surface of the rear-view mirror. Rear-view mirror 100
may include other elements, controls, or indicators on the border
of the mirror or on attached parts.
[0010] FIG. 2 is a side elevation view of a reflective backlit
display stack. Reflective backlit display stack 200 includes light
source 210, lightguide 220, prism film 230, first reflective
polarizer 240, liquid crystal cell 250, and second reflective
polarizer 260.
[0011] Light source 210 may be any suitable light source or
combination of light sources. Conventional light sources such as
light emitting diodes (LEDs), cold cathode fluorescent lamps
(CCFLs), and even incandescent bulbs may be used. In some
embodiments, although each light source 210 is depicted as a single
object in FIG. 2, combinations of LEDs (for example) may be used to
provide a sufficiently white input light, but, depending on the
application, any suitable spectrum or combination of spectra may be
utilized. Light source 210 may include suitable injection or
collimation optics to aid in coupling light into the structured
lightguide or to help shape the light input for the structured
lightguide. Light source 210 is disposed on either or both sides of
the lightguide. Light source 210 on either side may be the same or
similar light sources, or they may be different.
[0012] Lightguide 220 may be any suitable size and shape, and may
be formed from any suitable material by any suitable process. For
example, lightguide 220 may be acrylic or polycarbonate. Lightguide
120 may be formed from a process such as injection molding.
Lightguide 120 has at least one input edge. The input edge is
typically disposed on the surface of the lightguide closest to the
light source(s). The input edge may have any suitable shape or
structure, including structures to improve coupling of light from
the light source into the structured lightguide. Lightguide 220
also has one or more features for extracting light. These
extraction features may be arranged in any suitable configuration,
including a periodic pattern, a non-periodic pattern, or a
gradient. The extraction features may be arranged in a pattern that
increases the areal uniformity of light output from lightguide
220.
[0013] Prism film 230 is optional in constructions described herein
but may increase the overall on-axis brightness through light
recycling. In this case, a reflector (not shown) may be used to
redirect once again toward the front of reflective backlit stack
200 light that was reflected back from prism film 230 through total
internal reflection at the interface between the prism film facets
and air. The reflector may be coated on to lightguide 220 or may
not be present, where the reflective backlit stack simply relies on
Fresnel reflections off the interfaces of the prism films and
lightguides. In some embodiments, the reflector is a multilayer
optical film, such as Enhanced Specular Reflector (ESR) (available
from 3M Company, St. Paul, Minn.).
[0014] Prism film 230 has a plurality of prisms extending in a same
first direction. In some embodiments, prism film 230 may instead
have multiple films, with at least one film having prisms extending
in a first direction and at least one film having prisms extending
in a second direction orthogonal to the first direction. For
multiple prism films, they may be laminated to one another or may
simply rest on one another. The prism films may be formed by any
suitable process, including microreplication, for example through a
continuous-cast-and-cure process or the like.
[0015] The prisms of prism film 230 may have any suitable geometry,
including included angle, base angle, height, pitch, width, and
rotation--and one or more of these parameters may vary either along
a prism or across prisms. Prism film 230 may be, for example,
Brightness Enhancing Film (BEF) (available from 3M Company, St.
Paul, Minn.).
[0016] First reflective polarizer 240 and second reflective
polarizer 260 are disposed on either side of liquid crystal layer
250. Liquid crystal cell 250 typically includes a layer of liquid
crystal sandwiched by two layers of glass or another transparent
substrate. The reflective polarizers may both be adjacent to the
transparent substrate or one or both may be laminated directly to
the glass or transparent substrate of the liquid crystal cell. The
lamination may be performed using. Alternatively, only one or even
neither of the reflective polarizers may be laminated directly to
the glass or transparent substrate of the liquid crystal cell.
[0017] First reflective polarizer 240 may be any suitable
reflective type polarizer. In some embodiments, the reflective
polarizer may be an oriented multilayer polymeric optical film,
such as DBEF or APF reflective polarizers (available from 3M
Company, St. Paul., Minn.) In some embodiments, the reflective
polarizer may be a wire-grid or cholesteric reflective polarizer.
In some of these embodiments, the reflective polarizer may include
one or more retardation or compensation layers, such as a
quarter-wave plate, to convert between linear polarizations and
circular or elliptical polarizations. First reflective polarizer
240 may have any suitable thickness; in the case of a multilayer
optical film, the reflective polarizer may be a thicker
multi-packet or laminated construction or a relatively thinner
single packet construction. Second reflective polarizer 260 may be
identical to first reflective polarizer 240 or they may be similar.
In some embodiments, first reflective polarizer 240 and second
reflective polarizer 260 may have some or many different
characteristics. In some embodiments, an additional reflective
polarizer or reflective polarizers may be disposed on either or
both of the first and second reflective polarizers. In other words,
there may be two or more reflective polarizers on each side of the
First reflective polarizer 240 and second reflective polarizer 260
are configured to allow liquid crystal cell 250 to operate by
selectively gating light. Depending on the type of liquid crystal
material used in liquid crystal cell 250 (e.g., twisted nematic,
super twisted nematic, etc.) and how the liquid crystal cell is
electrically driven, the pass axes of the reflective polarizers
should be configured such that for a pixel in an "on" state--i.e.,
in a state where a voltage differential is generated across a pixel
of the liquid crystal cell, the light from the light source either
substantially passes through the second reflective polarizer or it
is substantially not transmitted through the second reflective
polarizer, and for a pixel in an "off" state--i.e., in a state
where there is no voltage differential across the pixel of the
liquid crystal cell, the light from the light source is treated
oppositely. Intermediate states are possible for certain types of
liquid crystal cells. This may be a parallel arrangement of the
pass axes of the reflective polarizers in some embodiments, or an
orthogonal arrangement of the pass axes of the reflective
polarizers. Any suitable driving electronics, conductive layers, or
thin film transistors (TFTs) may be included or integrated into or
included with liquid crystal cell 250.
EXAMPLE
[0018] The liquid crystal display for a SONY VAIO PCG-572N
(available from Sony Corp., Tokyo, Japan) notebook computer was
modified by removing, on one half only, the absorbing polarizers
laminated to either side of the glass of the liquid crystal cell.
After removing the absorbing polarizers on half of the display, the
absorbing polarizers were replaced by laminating 3M APF-T35
reflective polarizers (available from 3M Company, St. Paul, Minn.)
to the glass. The liquid crystal display was replaced and observed
in both an "ON" (displaying an image) and "OFF" (displaying no
image) state. The modified portion of the liquid crystal display
functioned as a reflective backlit display, functioning as a mirror
when the display was OFF and showing a viewable image when the
display was ON.
[0019] Performance was acceptable when compared to the reference
half of the display, especially considering the reference display
would further require a vapor-coated partial mirror to function as
a reflective backlit display.
[0020] The following are exemplary embodiments according to the
present disclosure:
Item 1. A reflective backlit display, comprising: [0021] a
backlight; [0022] a liquid crystal cell including a liquid crystal
layer disposed between two opposing transparent substrate layers;
[0023] a first reflective polarizer; and [0024] a second reflective
polarizer; [0025] wherein the first and second reflective
polarizers are each directly adjacent to one of the opposing
transparent substrate layers. Item 2. The reflective backlit
display of item 1, wherein at least one of the first or second
reflective polarizers is a multilayer reflective polarizer. Item 3.
The reflective backlit display of item 1, wherein each of the first
or second reflective polarizers is a multilayer reflective
polarizer. Item 4. The reflective backlit display of item 3,
wherein the two transparent substrate layers are glass. Item 5. The
reflective backlit display of item 1, wherein the first and second
reflective polarizers are each directly laminated to one of the
opposing transparent substrate layers. Item 6. The reflective
backlit display of item 1, wherein the backlight includes a
lightguide, a reflector disposed on the light guide, and a light
source configured to inject light into the lightguide. Item 7. The
reflective backlit display of item 1, further comprising a third
reflective polarizer, wherein the third reflective polarizer is
disposed on either the first or the second reflective polarizer.
Item 8. A mirror, comprising: [0026] a mirror portion; and [0027] a
reflective backlit display portion comprising the reflective
backlit display of item 1; [0028] wherein the reflective backlit
display is capable of directly displaying images, and the mirror
portion is not. Item 9. A vehicle, comprising the mirror of item 8,
the mirror being configured as a rear-view mirror. Item 10. The
mirror of item 9, wherein the reflective backlit display portion is
greater than 10% but less than 50% of an area of the mirror. Item
11. The reflective backlit display of item 1, wherein the
reflective backlit display includes no absorbing polarizers. Item
12. The reflective backlit display of item 1, wherein the
reflective backlit display includes no non-polarization-dependent
partial reflector.
* * * * *